FAA Commercial Pilot Airplane (CAX)RegulationsEasy
An aircraft owner asks a mechanic when the emergency locator transmitter (ELT) battery must be replaced or recharged. According to 14 CFR 91.207, the battery must be replaced after how much cumulative time in use, or when what percentage of its useful life has expired, whichever occurs first?
- A4 hours of cumulative use, or 50 percent of its useful life
- B6 hours of cumulative use, or 50 percent of its useful life
- C1 hour of cumulative use, or 50 percent of its useful life
- D1 hour of cumulative use, or 25 percent of its useful life
Show answer & explanationAnswer & explanation
Correct answer: C. 1 hour of cumulative use, or 50 percent of its useful life
14 CFR 91.207(c) requires ELT batteries to be replaced (or recharged if rechargeable) after 1 cumulative hour of use, or when 50 percent of their useful life (or, for rechargeable batteries, 50 percent of their useful life of charge) has expired, whichever comes first.
Why the other options are wrong
- A. 4 hours is not the correct threshold under 91.207
- B. 6 hours overstates the 1-hour cumulative-use limit
- D. 25 percent understates the actual 50 percent threshold
ELT Battery Replacement (91.207)
ELT batteries must be replaced after 1 cumulative hour of use or 50% of useful life, whichever occurs first.
- 1 hour cumulative use limit
- 50% useful life limit
- New expiration date must be marked on the ELT
Memory trick: 'One hour, half life' — 1 hour used or half the battery's life, whichever comes first.